Acura RSX EPS Warning Light Retrofit and DTC Communication Enable
Introduction
An RSX that has had an EPS (electric power steering) system fitted normally has no dashboard telltale for that system, so when the EPS control logic sets a DTC and shuts the assist down, the driver gets no indication and there is no lamp for a scanner to communicate with the BCU. That gap leads owners to swap the BCU on guesswork, often without fixing anything. This retrofit closes it by grafting an EPS indicator LED and its logo into the RSX instrument cluster and wiring the diagnostic lines so the system behaves like factory: the telltale lights with the ignition, clears within about two seconds when no faults are stored, and gives a path to read codes and reset the BCU. It applies to 2002-2006 Acura RSX (DC5) that carry an EPS setup, using cluster parts and the connector pinout from a 2002-2005 Honda Civic Si (EP3) or 2003-2005 Honda Civic Hybrid (EM2), whose factory manuals share identical wire colors and codes. Adapted from a community writeup by Cloneufc on Club RSX (https://www.clubrsx.com/threads/diy-eps-warning-light-conversion-and-eps-dtc-retrieval-functionality.1274219/), including corrections from the follow-up discussion.
Reference
Tools Required
- Tin snips
- Soldering iron
- Rosin-core solder
- Flux (Kester)
- 3M electrical tape
- Heat-shrink tubing
- Heat gun
- Super glue or emblem adhesive
- Razor blade or box cutter
Parts Required
-
EPS logo salvaged from a cluster equipped with EPS (02-05 Civic Si EP3 or 03-05 Civic Hybrid EM2)
-
One indicator LED from a spare cluster (keep 4-5 spares, since some fail during soldering)
-
3 lengths of roughly 3.5ft wire, matched gauge (OEM salvage wire preferred)
Safety Warnings
- ⚠ LED polarity must be correct or the telltale will not light; the board's triangle/arrow at the 5 o'clock mark indicates the negative leg.
- ⚠ Disconnect the battery before splicing into the cluster harness and the DLC to avoid shorts while working live circuits.
- ⚠ Insulate all splices with heat-shrink and tape so the added leads cannot chafe or short against the dash structure.
Step-by-Step Instructions
1 Harvest the donor telltale and LED
From a cluster that already carries an EPS indicator, reclaim the EPS logo and one working indicator LED. An 02-05 Civic Si (EP3) or 03-05 Civic Hybrid (EM2) cluster both serve, because their factory wiring and color coding match. Pull four or five spare LEDs as well, since soldering heat destroys some. The white cap covering the plate is not required.
2 Remove and open the RSX cluster
Extract the RSX instrument cluster from the dash and split its housing so the printed face, front lens, and circuit board are all accessible. This teardown is specific to the car; if you have not done it before, follow a dedicated RSX cluster-disassembly reference rather than improvising.
3 Solder leads to the salvaged LED
Solder a lead onto each leg of the reclaimed LED, leaving both long enough to exit the rear of the reassembled cluster; cut three roughly 3.5ft lengths of matched-gauge wire for this. Respect polarity: a triangle or arrow etched near the 5 o'clock mark on the board points to the negative leg. Although that leg is fed by a live source at the LED, it ultimately terminates at ground through the BCU.
4 Trim the LED board into the spare indicator slot
Cut the salvaged LED's circuit board down with tin snips until it seats in the empty indicator position, which sits just above the odometer LEDs. Confirm the odometer still closes and pare away anything that fouls it. Fasten the board with its screw and hold it with adhesive or by clamping it under pressure; fine-center the LED from the front of the cluster if needed.
5 Bond the EPS logo over the opening
Cut the EPS emblem free. On the white inner face, dry-fit the logo over the indicator opening, then run emblem adhesive only around its edge so light passes through the center. Leave the middle unglued and keep it centered over the slot.
6 Open a matching window in the gauge face
Measure the emblem and cut an opening of the same size in the printed gauge face with a box cutter so the telltale reads through. Lay the face back into position without adhesive, close the cluster up, and route both LED leads out the back.
7 Mount the cluster loosely and land the indicator wires
Reinstall the cluster but leave it standing proud of the dash so the harness stays within reach. Connect the marked-negative LED lead to C6 YEL/BLU, the EPS warning-light line on the Civic Hybrid C connector. Feed the positive LED lead from the cluster harness power wire: B7 Yellow on 02-04 RSX, or B6 Yellow on 05-06 RSX, both supplied through Fuse 10 under the dash.
8 Expose the data link connector
Find the OBD-II data link connector on the driver side, beneath the under-dash fuse box. Press the two clip tabs and free the connector by hand; no tool is needed. Take out the 10mm bolt on the adjacent rod and move the rod aside to reach the release clip.
9 Splice the diagnostic communication lines
On the rear of the DLC, tap the brown wire and run it to C8 BRN, the service check signal on the Civic Hybrid C connector. Tap the gray wire and run it to C20 GRY, the Diagnosis-H communication line. These two links give the retrofit a scan path to retrieve and clear codes and reset the BCU.
10 Reseat the cluster and verify function
Insulate and weatherproof every splice with heat-shrink and tape, then push the cluster fully home. With the ignition on, the EPS telltale should illuminate. After the engine starts it should go dark within roughly two seconds when no codes are stored; a lamp that stays lit signals a stored DTC to pull.
Pro Tips
- 💡 The EP3 Civic Si and EM2 Civic Hybrid clusters share the same wires and color coding per both factory repair manuals, so either is a valid donor.
- 💡 Keep four or five spare LEDs on hand because the soldering heat can kill some of them.
- 💡 Prefer matched-gauge OEM wire pulled from a wrecking yard for the three leads so the run stays consistent.
- 💡 If the LED sits slightly off-center after assembly, you can adjust it from the front face of the cluster.
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